Ice dam risk in Aberdeen, SD
Will your roof get ice dams in Aberdeen, SD?
30.2 dam days a winter
High risk. On an ordinary house in Aberdeen, conditions for an ice dam come on about 30.2 days in a normal winter, mostly in January and February.
Aberdeen averages 43 inches of snow a year and about 80 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
What your attic does to that number in Aberdeen
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 12.4 | Moderate |
| Typical, some insulation, not air-sealed | 30.2 | High |
| Older or poorly insulated, warm attic | 52.4 | Severe |
Sealing and insulating a typical attic takes out about 17.8 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 52.4 days.
Preventing ice dams on a Aberdeen roof
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
- Rake the bottom three or four feet of roof after any storm that leaves more than about six inches, from the ground with a roof rake.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
Which to spend on first: air sealing or heat cable.
Aberdeen winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 7.8 | 24.0 | 10.4 |
| February | 8.6 | 18.2 | 7.3 |
| March | 6.3 | 12.4 | 3.6 |
| April | 4.2 | 2.3 | 0.3 |
| October | 1.3 | 0.7 | 0.1 |
| November | 6.5 | 5.7 | 1.7 |
| December | 8.0 | 16.9 | 6.8 |
Aberdeen next to nearby towns
Aberdeen ranks 3 of 14 South Dakota cities here for ice-dam days, behind Watertown at 35.4 days.
- Watertown, SD 75 mi, 35.4 days
- Huron, SD 77 mi, 26.4 days
- Jamestown, ND 100 mi, 45.7 days
- Brookings, SD 115 mi, 31.5 days
- Pierre, SD 118 mi, 21.9 days
Where these numbers come from
NOAA 1991–2020 climate normals from Aberdeen, 2.7 miles from Aberdeen. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.